In September 1978 Ali was the most famous man on Earth - bar none. Young Michael Gerard Tyson was a nobody sitting in a juvenile detention centre in New York after being arrested for purse-snatching.

Now Tyson is arguably as big a name worldwide as Ali, whose modern-day image is of a noble, almost saintly figure travelling the globe spreading good will.

Afflicted with but unbowed by Parkinson's Disease, Ali has lost his magical tongue and is shorn of the rabble-rousing image which inspired either love or loathing.

Tyson inspires the same extreme reactions, although with him they are caused more by his actions than his words.

Ali, now 58, refuses the notion that he is deserving of pity

Tyson, a convicted rapist who has also served time for a "road rage" attack, fights Britain's Julius Francis in Manchester on 29 January. Security will be tight.

Similar passions were inflamed when Ali came to Lewiston, Maine, in 1965 for his second bout with Sonny Liston.

Ali, who had taken Liston's world title the previous year in Miami, had recently converted to Islam.

With civil rights protests across the US and racial mistrust at its height, his denouncements of the white establishment made him a serious target for assassination.

Writers, like Norman Mailer and Robert Lipsyte, who covered Ali's first round victory - recall policemen scanning the crowd as if they expected an assassin's bullet at any minute.

The people of Brixton showed their true feelings. People of all ages and races, and a lot of women, turned out and loved him.

Tyson's promoter Frank Warren

If Tyson gets to fight undisputed champion Lennox Lewis - and win - he will join Ali and Evander Holyfield as the only men to win the world title three times.

Their characters could not be more different, but Tyson's visit to Brixton in south London on Friday was another echo of Ali - boxing's elder statesman visited the black community there last year.

Next weekend's fight will be Tyson's first in the UK and it is too early to say if it will bear any similarities to Ali's British battles.

In 1963, against Henry Cooper, he survived being hit by 'Enry's 'ammer, and came back to stop the British champion in the fifth.

Three years later he repeated the act at Highbury stadium, stopping Cooper in the sixth round.

That same year he came back to London, knocking out the hapless Brian London in the third.

Ali and Tyson have always been extremely conscious of their skin colour, although they grew up in different eras and environments.

Ali, born Cassius Marcellus Clay on 17 January 1942, was raised in the "black end of town" in Louisville, Kentucky and quickly became aware of the daily depredations and humiliations forced on his "brothers"..

Ali's fights Henry Cooper in 1966

When he came back from winning Olympic gold in 1960, Clay was refused service by a white waitress in a Louisville diner.

The myth has it that he threw away his medal in disgust. In fact he had lost it a few days before. But whatever the truth, there was no doubting the feeling of alienation.

Black civil rights were becoming a key issue but rather than side with the moderate Reverend Martin Luther King, Ali chose to align himself with Malcolm X and the Nation of Islam.

Desiree Washington was Tyson's downfall

Thirty years later Tyson also sought spiritual guidance from America's black Muslims during his time of need.

Tyson converted to Islam after being sent to jail in Indiana in 1992 for raping Desiree Washington, a contestant at the Miss Black America pageant the previous year.

He has always maintained his innocence, claiming Ms Washington consented to sex.

Many of those who turned up in Brixton to give him a hero's welcome believe his denials.

Julius Francis, pictured with Sports Minister Kate Hoey, is playing the Henry Cooper role

Ali had his own high-profile brush with the law.

Unlike Tyson, it was caused by high principle rather than low animal lust.

In 1966, as President Lyndon Johnson stepped up America's involvement in the Vietnam war, the former Olympian shocked the US by declaring: "I ain't got no quarrel with them Viet Cong."

It was no empty rhetoric. In May 1967 he was indicted by a federal grand jury in Houston, Texas after refusing the draft.

The following month Ali - as he was now known - was convicted of draft evasion, fined $10,000 and sentenced to five years in prison.

But his lawyers appealed against the conviction and, as the legal arguments dragged on, Ali was stripped of his world title.

Ironically it was while the monolithic Ali was away from the ring that the world title splintered, with the WBA breaking away from the WBC and later spawning the IBF.

The crown remained divided for nearly two decades until another colossus entered the ring - "Iron" Mike Tyson.

In 1986, at the age of 20 years and 144 days, he took two rounds to win the WBC title. The man he deposed was Trevor Berbick, the same man who had beaten an ageing Ali in his last contest in 1981.

He went on to wrench the WBA title and destroyed the highly respected Michael Spinks - brother of former Ali conqueror and victim Leon - to gain the IBF belt.

The title was unified at last.

Tyson takes a chunk out of Evander Holyfield's ear

Tyson was at his peak but his mask of invincibility slipped in 1990 when he suffered one of the most shocking defeats in boxing history - against 16-1 underdog James "Buster" Douglas.

The bout came only months after the collapse of his disastrous marriage to TV and film star Robin Givens, whom he had married in 1988.

The fairer sex was also Ali's Achilles heel. He once described womanising as his only vice and said it was the only thing that prevented him being a good Muslim.

Ali tied the knot four times.
He married his first wife, cocktail waitress Sonji, in 1964 but she could not cope with the strict dress code imposed on women by the Nation of Islam.

Three years later the newly divorced Ali married 17-year-old Belinda Boyd, who changed her name to Khalilah, and they had four children.

Mike's very deep...Ask him about philosophy and you're in for a treat. Ask him about Nietzsche, that's his man!

Tyson's trainer and friend Jay Bright

But the marriage did not last and by 1977 Ali had wed model Veronica Porche - one of his children by her was Laila, who has recently started her own career as a boxer.

In 1985 he divorced Laila's mother and now lives with his fourth wife Lonnie.

Tyson, now 34, seems to have found happiness with second wife Monica Turner, a paediatric doctor.

They have two children, Rayna and Amir, as well as two from their previous relationships and Tyson often says he is fighting to provide a good start in life for them.

One can only hope Tyson does not repeat the final mistake Ali made by prolonging his career too long.